1. Field of the Invention
The present invention relates to a mobile communication system based on the principles of CDMA (Code Division Multiplex Access), and more particularly to a receiving circuit in a mobile terminal in a mobile communication system based on the principles of CDMA.
2. Description of the Related Art
In recent years, mobile communication systems are finding a growing number of subscribers and are required to increase their capacity to accommodate subscribers. One approach to an increased capacity to accommodate subscribers is a technique known as CDMA in which one frequency band is shared by signals spread by a plurality of mathematically orthogonal codes.
In a CDMA mobile communication system, the receiving circuit of each mobile terminal has a plurality of finger receivers for inversely diffusing transmitted data in association with respective multiple paths. The transmitted data are inversely diffused by the finger receivers and then synthesized with each other.
FIG. 1 of the accompanying drawings shows in block form a receiving circuit in a mobile terminal in a conventional mobile communication system.
As shown in FIG. 1, the receiving circuit comprises an antenna 1 and a radio unit 2 for receiving data, a plurality of finger receivers 3-1 through 3-n associated with respective multiple paths, for inversely diffusing the data received via the antenna 1 and the radio unit 2, a maximum ratio synthesizer 4 for synthesizing the data inversely diffused by the finger receivers 3-1 through 3-n, a search engine 5 for detecting respective components of the multiple paths, a timing controller 7 for controlling the timing of operation of the finger receivers 3-1 through 3-n, and a CPU 6 for controlling operation of the timing controller 7 based on the components detected by the search engine 5.
The receiving circuit shown in FIG. 1 operates as follows: When data is received by the antenna 1 and the radio unit 2, the data is inversely diffused by the finger receivers 3-1 through 3-n, and thereafter the inversely diffused data are synthesized by the maximum ratio synthesizer 4 into data which is outputted to a subsequent circuit (not shown).
When data is received by the antenna 1 and the radio unit 2, all the finger receivers 3-1 through 3-n are in operation.
In the conventional receiving circuit, however, since the all the finger receivers 3-1 through 3-n operate even if the received data contains no speech signal, the receiving circuit causes a wasteful consumption of current when the received data contains no speech signal.